ABSTRACT Support is requested for a Keystone Symposia meeting entitled Type I Interferon: Friend and Foe Alike, organized by Drs. Alan Sher, Virginia Pascual, Adolfo Garca-Sastre and Anne O'Garra. The meeting will be held in Banff, Alberta, Canada from March 19-23, 2017. While cytokines play critical roles in host defense and immune homeostasis, they in other settings can be key mediators of inflammatory pathology. This important functional dichotomy is perhaps best exemplified in the diverse activities of Type I interferon(s) in health and disease. Type I IFNs regulate a broad family of genes that either stimulate or inhibit immune function and in so doing have host protective or detrimental effects. Thus, while Type I IFNs are well-known for their anti-viral activity and stimulation of effector T cell responses, they can also promote autoimmune, bacterial and even certain viral diseases. Understanding this contextual dependency is crucial for unraveling the pathogenesis of Type I IFN-dependent diseases and for the design of interferon-based therapies and will be the central focus of the meeting. This conference will open with talks presenting an overview of Type I IFN genes and their regulation, innate recognition mechanisms and signaling pathways for Type I IFN induction and Mendelian- based interferonopathies. Additional sessions will focus on the role of Type I IFN in viral, bacterial and autoimmune diseases. The meeting will conclude with a discussion of the mechanistic and contextual factors that determine the beneficial versus deleterious outcome of Type I IFN induction and how this information can be applied to the development of targeted therapeutic interventions. Because of the timeliness of the topic, the conference should draw a broad audience from the fields of cytokine biology, inflammation, infectious disease and translational medicine and attract a solid industry representation. Opportunities for interdisciplinary interactions will be significantly enhanced by the concurrent meeting on Pattern Recognition Signaling: From Innate Immunity to Inflammatory Disease, which will share a keynote address and plenary session with this meeting.